Method of making electrical conductor cables



Aug. 23, 1949. R. GILLIS METHOD OF MAKING ELECTRICAL CONDUCTOR CABLESFiled April 25, 1944 Patented Aug. 23, 1949 METHOD F MAKING ELECTRICALCONDUCTOR CABLES Randall Gillis, Westeld, N. J., assignor to WesternElectric Company, Incorporated, New York,

N. Y., a corporation of New York Application April 25, 1944, Serial No.532,614 2 Claims. (Cl. 154-225) This invention relates to electricalconductor cables and a method of making the same. and more particularlyto electrical conductor cables of relatively light weight yet providedwith gastight and liquid-tight metallic sheathing, and to a method ofmaking these.

Electrical conductor cables have long been made successfully andsatisfactorily having sheaths continuously seamless both longitudinallyand circumferentially of lead -or one or another metallic alloycomprising lead as principal ingredient. Such sheaths are eminentlysatisfactory and suitable in every Way except that they are necessarilyboth bulky and heavy. Owing to the relative softness and ductility oflead and of the lead alloys suitable for this purpose, cable sheaths ofsuch material for mechanical strength in themselves and for mechanicalprotection to the cable cores which they enclosed, must be considerablythicker than is necessary to provide a merely gas-tight, moistureproofsheath.

An object of the present invention is to provide a cable structure whichwill enable the substitution for the seamlessly extruded but heavy leadmaterial sheaths of metallic sheathings of copper, brass, iron or othermetallic material not comprising any appreciable amount of lead whichshall yet be substantially as flexible in use and as fully protective aslead sheaths while being materially less in weight.

With the above and other objects in view, the invention may be embodiedin an electrical cable having a core, protective means for the corecomprising a metal sheath having a longitudinal soldered seam thereinand formed over the core, a substantially seamless layer ofthermoplastic and impervious substance formed over the metal sheath, anda second metal sheath having a longitudinal soldered seam therein andformed over the layer, the seams of the two metal sheaths being spacedwell apart circumferentially of the cable.

Other objects and features of the invention will appear from thefollowing detailed description of an embodiment thereof taken inconnection with the accompanying drawing, in which the same referencenumerals are applied to identical parts in the several iigures and inwhich Fig. 1 is a view in side elevation of a, piece of electricalconductor cable constructed in accordance with the invention; and

Fig. 2 is a transverse section of the same.

In the embodiment of the invention herein disclosed, the cableillustrated comprises a conductivecore I Il of which no particularstructure is shown or described since the specific structure of this isirrelevant to the invention proper which pertains to the sheathing ofsuch a core. the core I0 is, preferably, a helical wrapping II ofinsulating material, e. g. paper, in tape form 1 material of it althoughthis wrapping may be omitted in some instances. Over the wrapping II isa seamless layer of suitable insulating substance, e. g. an asphalticmaterial, a mineral wax composition, a composition comprising rubber,gutta percha, or the like, or other analogous sheathing stun. Over thelayer I2 is a metallic sheath I4. This is formed by folding atransversely corrugated, thin tape, of suitable metallic substance,about the previously described unitarystructure, the axis of the tape asa whole being parallel to the axis of the core, and the edges of thetape being brought together, preferably overlapped as shown, and joined,e. g. by soldering or brazing, along a closure seam I5 runninglengthwise of the sheath and substantially parallel to the axis of thewhole. The material of the metal tape of which the sheath I4 is formedis preferably copper, brass, bronze, iron, aluminum or other similarmetallic substance materially lighter and tougher than the leadmaterials often used. As shown here, the circumferential empty spaces orvoids I3 formed between the layer I2 and the sheath I4 by thecorrugations of the latter, are left unfilled. The corresponding valleysI6 on the outside of the sheath I4, however, are preferably filled, e.g., with rubber asphalt cement, or the like, to provide a smoothlycylindrical surface I'I upon which to form the next element I8 of thestructure, which is a layer I8 of thermoplastic material.

This layer I8 is an important feature in the combination comprised inthe invention. The

' should be water repellant and water and vapor tight. It should remainsoft and not subject to cracking when bent at low temperatures, say downto well below the temperature of freezing water, and-should not softenand flow 'unduly when kept for longer periods at tempertures of theorder of F. On the other hand, it should be weldable when exposed for abrief interval to the heat occasioned by soldering or brazing the yet tobe described metal sheath surrounding it as hereinafter related. Variouscompounds or compositions are known in the art which are suitable forthis purpose, having the properties described. As an example, thecomposition made by compounding Parts by weight Reclaimed natural rubber40 The hard hydrocarbon commercially known as mineral rubber 12 Clay 43Cumar resin 4 Parafiin i 1 is an eminently suitable composition for thelayer I8. This can be formed into a solid, relatively tough andmanageable tape at ordinary temperatures, which is appliedlongitudinally over the asphalt rubber cement filling I1 and folded intoA a tube with the edges of the tape abutted iirmly a molten compoundwhich is both an adhesivev and a soldering ilux. One suitable compoundfor this purpose and having the desired properties consists f y Rosin-per cent by weight-- 25 to 75 Rosin oil -do 20 to 50 Polymerizedisobutylene ....per cent-- to 25 A suitable compound for the layers orcoatings I2 and I1 may be made by softening the compound suggested abovefor the layer I8 with a mixture of asphalt, mineral oil and rosin oiluntil the desired consistency is obtained.

The corrugated metal tape to form the sheath Il, the thermoplastic tapeto form the layer I8 and the corrugated metal tape to form the sheath2li are applied in each case in such a way that the seam I5 of thesheath I4 and the seam I9 of the layer I8 are on opposite sides. Thetape to form the sheath 20, however, is so applied that the overlap ofits edges forming the seam 23 lies directly overand along the seam I9 ofthe layer I8. When the seam 23 is soldered in the manufacture of thecable, the heat of the soldering causes the edges of the tape in thelayer I8 to weld together. Thus in the completed cable, the solderedseams I5 and 23 of the two metal sheaths I4 and 20 are on opposite sidesof the cable as well as having the practically seamless layer I8 betweenthem. If there should be or should develop flaws in the soldered seamsI5 and 23 or in the welded seam I9, the imperviousness of thecombination of the three elements I4, I8 and 20 will ordinarily be fullymaintained, even if the filler I'l for the corrugation valleys I6 wereomitted, since the chance of leaks appearing or developing in the threeseams at points located in the same corrugation valley I6 is prac`tically negligible and the corrugations between the valleys I5 andbetween the valleys 2I ordinarily prevent any leakage longitudinally ofthe cable even without the filling I1 and 22.

The simplest way to make the layer I8, in commercial manufacture, isthat described above, by folding av tape about the core and welding itsedges to close the seam I9, and such method of manufacture and thestructure resulting therefrom will ordinarily be entirely satisfactory.However, where extreme assuredness of imperviousness is desired, e.'g.,where a cable is to serve under high external pressure of gas, vapor orliquid, the layer I8 may be created wholly seamlessly by extrusion.

As noted above, in the process of manufacture, the adhesive flux 22 isapplied molten to the inner surface of the tape 20 while the latter isbeing formed around the layer I8. It is contemplated that the seam 23will be soldered immediately the edges of the tape are overlapped andwhile the adhesive flux is still molten and provides no bar to thetransfer of excess soldering heat therethrough to weld the seam I9. l

Apparatus for carrying on the various steps of manufacture describedform 'no part of the present invention, but such apparatus is variouslydescribed and claimed in copending applications Serial No. 532,613, nowPatent No. 2,459,877, January 25, 1949, by the present inventor, andSerial No. 532,612, now abandoned, by the present inventor and another,filed of even date herewith, and to which reference may be had ifdesired.

It will be evident that so far as the cable itself and its embodiment ofthe invention are concerned, the nature of the structure enclosed withinthe sheath I4 is not material in any way provided that it contain one ormore electrical strands. Hence in the appended claims the word core willbe taken to mean any kind of electrical cable core to which thecombination of the i invention may be applicable. The completedstructure as above described may be used in some instances withoutfurther added elements. Ordinarily, however, the metal sheath 20 will becovered with some further outer covering 24 whose nature and mode ofapplication are irrelevant here.

Ordinarily the seam I5 and the seam 23 will be closed and sealed bysoldering with one or another of the well known alloys, principally oflead and tin, used for such purpose. In some instances it may bedesirable or necessary to close one or the other or both of these seamsby brazing or welding. It is intended that the words soldering soldered"and the like in the appended claims shall be taken to mean any suitablemeans of sealing these seams with molten metal.

What is claimed is:

1. The method of making an electrical conductor cable which comprisessteps of forming a tape of metal into a sheath about a conductive cablecore with the two edges of the tape forming a seam.runninglongitudinally along the core, soldering the edges of the tape togetherto seal the seam formed thereby, forming a tape of thermoplasticsubstance about the soldered metal sheath into a layer enclosing thesame and with the seam thereof spaced circumferentially of the core fromthe seam of the metal sheath, applying a second metal tape over` thelayer and covering the seam of the first metal sheath, forming thesecond metal tape into a sheath about the layer with the two edges ofthe tape forming a seam running longitudinally of the core and spacedoircumferentially of the core from the seam of the rst metal tape andlying directly on the seam of the tape of thermoplastic substance, andsoldering the edges of the tape together to seal the seam formed therebywhile also causing the edges of the tape of thermoplastic substance tobe welded together by the heat of the soldering operation.

2. The method of making an electrical conductor cable which comprisessteps of forming a tape of metal into a sheath about a conductive cablecore with the two edges of the tape forming a seam runninglongitudinally along the core, soldering the edges of the tape togetherto seal the seam formed thereby, forming a tape of thermoplasticsubstance about the soldered metal sheath into a layer enclosing thesame and with the seam thereof spaced circumferentially of the core fromtheseam of the metal sheath, applying a transversely corrugated secondmetal tape over the layer and covering the seam of the first metalsheath, lling the corrugations on the inner side of the second metaltape with adhesive 'iiux material while applying the tape to the core,

forming the second metal tape into a sheath about the layer with the twoedges of the tape forming a seam running longitudinally o1' -the coreand spaced circumferentially of the core from the seam of the rst metaltape and lying directly on the seam of the tape of thermoplasticsubstance, and soldering the edges of the tape together to seal the seamformed thereby While also causing the edges of the tape of thermoplasticsubstance to be welded together by the heat of the soldering operation,

RANDALL GILLIS.

REFERENCES CITED 'I'he following references are of record in the le ofthis patent:

Number Number 6 UNITED STATES PATENTS Name Date Tainter Dec. 4,1883 ReadJuly 17, 1917 Knoderer Nov. 4,1924 Specht s July 27, 1937 Boe Aug` 24,1937 Eckel Oct. 1, 1940 Mougey May 18, 1943 FOREIGN PATENTS Country DateFrance Dec. 26, 1938

